Life Sciences Grade 12 P1 NSC November 2018 Memo (English)

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE GRADE 12 LIFE SCIENCES P1 NOVEMBER 2018 MARKING GUIDELINES MARKS: 150 These marking guidelines consist of 9 pages. Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 2 DBE/November 2018 NSC – Marking Guidelines SECTION A QUESTION 1 1.1 1.1.1 B 1.1.2 B 1.1.3 D 1.1.4 C 1.1.5 C 1.1.6 A 1.1.7 B 1.1.8 C 1.1.9 A 1.1.10 C (10 x 2) (20) 1.2 1.2.1 Amniotic egg 1.2.2 Precocial development 1.2.3 Cerebellum 1.2.4 Choroid 1.2.5 Corpus callosum 1.2.6 Hypothalamus 1.2.7 Carbon dioxide/CO 2 1.2.8 Tropisms 1.2.9 Weed-killer/herbicide 1.2.10 Poaching (10) 1.3 1.3.1 None 1.3.2 A only 1.3.3 Both A and B (3 x 2) (6) 1.4 1.4.1 Fertilisation (1) 1.4.2 Mitosis (1) 1.4.3 - Chorion - Amnion (Mark first TWO only) (2) 1.4.4 (a) Zygote (1) (b) Morula (1) (c) Blastocyst/blastula (1) 1.4.5 Fallopian tube (1) 1.4.6 47 (1) (9) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 3 DBE/November 2018 NSC – Marking Guidelines 1.5 1.5.1 (a) Pituitary/hypophysis (1) (b) Thyroxin (1) 1.5.2 Negative feedback mechanism (1) 1.5.3 - Less hormone B/thyroxin will be secreted - More hormone A/TSH will be secreted (Mark first TWO only) (2) (5) TOTAL SECTION A: 50 Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 4 DBE/November 2018 NSC – Marking Guidelines SECTION B QUESTION 2 2.1 2.1.1 (a) Prophase I (1) (b) Anaphase I (1) 2.1.2 Cells formed at the end of meiosis Criteria for marking Only two cells have been drawn (D) 1 mark Each cell contains only two un-replicated 1 mark chromosomes (C) Each chromosome is the correct size and 1 mark correctly shaded (S) Any TWO correct labels 2 marks (5) (7) 2.2 2.2.1 - Needed for spermatogenesis - Stimulates the development of secondary male characteristics/deeper voice/facial hair/body hair/increased muscle mass/increase in size of the sex organs/sex drive (Mark first ONE only) Any (1) 2.2.2 - Administering testosterone/hormonal treatment - Surgery (2) (Mark first TWO only) 2.2.3 33⅓ % (1) 2.2.4 It increases the risk of testicular cancer (1) (Mark first ONE only) 2.2.5 - The temperature of the testes will be too high/poor blood circulation/increased pressure on the testes - therefore sperm will not mature/spermatogenesis will be negatively affected (2) (7) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 5 DBE/November 2018 NSC – Marking Guidelines 2.3 2.3.1 To calculate BMI (1) 2.3.2 41/100 x 1510 = 619 (Accept 619,1) (3) 2.3.3 Only women with planned pregnancies will know how long it took them to fall pregnant (2) 2.3.4 All the women: - were the same age/between the ages of 20 and 30 years - were pregnant for the same amount of time/at least 20 weeks pregnant - had planned to fall pregnant - had conceived naturally (Mark first ONE only) (1) Any 2.3.5 (2) Do not smoke if your BMI is <20 or ≥30 2.3.6 - Similar/same results were obtained (2) - in the second/repeated investigation (11) 2.4 2.4.1 (a) Transmits sound waves to the tympanic membrane/Secretes ear wax (1) (Mark first ONE only) (b) Equalises pressure on either side of the tympanic membrane (1) (Mark first ONE only) (c) Releases pressure from the inner ear (1) (Mark first ONE only) 2.4.2 (a) C (1) (b) D (1) 2.4.3 - The receptors cannot convert the stimuli into impulses - No impulses/fewer impulses are transmitted to the cerebrum - and the person does not hear anything/hearing is impaired (3) 2.4.4 - The sound vibrations are transmitted from the large tympanic membrane - to the smaller oval window - through the ossicles - which are arranged from largest to smallest - This concentrates the vibrations, amplifying them Any (3) 2.4.5 - A change in speed/direction of movement - stimulates the cristae - The stimulus is converted to an impulse - The impulse is transmitted to the cerebellum - via the auditory nerve - The cerebellum sends impulses to the muscles to restore balance Any (4) (15) [40] Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 6 DBE/November 2018 NSC – Marking Guidelines QUESTION 3 3.1 3.1.1 Auxins (1) 3.1.2 (a) Light (1) (b) Gravity (1) 3.1.3 Plant structure B has bent towards the light/towards A/positively phototropic (1) 3.1.4 - Auxins accumulated on the lower side of the root - The high concentration of auxins on the lower side of the root inhibits growth - The lower concentration of auxins on the upper side stimulates growth - causing uneven growth/the root to bend downwards/positive geotropism Any (3) (7) 3.2 3.2.1 A (1) 3.2.2 The impulse does not travel to the brain/goes directly from receptor to effector via the spinal cord (1) 3.2.3 - Allows the person to respond rapidly - and without thinking/involuntarily - to a stimulus - to prevent damage to the body* 1* compulsory + any other 2 (3) 3.2.4 Nerve/spinal cord (1) 3.2.5 - It acts as an insulator - and therefore, speeds up the nerve impulse/prevents a short circuit (2) 3.2.6 - The person would be able to feel the stimulus - but would be unable to react - because the impulse would not be transmitted to the effector Any (2) 3.2.7 - The receptor receives the stimulus - and converts it into an impulse - which is transported by a sensory neuron via the spinal cord - to the brain*/cerebrum - The brain/cerebrum interprets the impulse* - The brain/cerebrum sends an impulse to a motor neuron - which conducts the impulse to the effector - to bring about a response 2* compulsory + any other 4 (6) (16) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 7 DBE/November 2018 NSC – Marking Guidelines 3.3 3.3.1 The level increases (1) T 3.3.2 Fewer larger meals More smaller meals 1. Maximum blood insulin 1. Maximum blood insulin concentration is concentration is higher/between 160-180 lower/between 120-140 mg/dl mg/dl 2. Minimum blood insulin 2. Minimum blood insulin concentration is concentration is higher/40 lower/between 20-30 mg/dl mg/dl 3. Blood insulin concentration 3. Blood insulin concentration rises and falls three times a rises and falls six times a day/less often day/more often 4. Large changes in insulin 4. Small changes in insulin concentration/between 140- concentration/between 80- 160 mg/dl 100 mg/dl 5. Insulin concentration drops 5. Insulin concentration varies below minimum glucose above and below minimum concentration glucose concentration (Mark first TWO only) 1 for table + Any 2 x 2 (5) 3.3.3 - A diabetic may not produce sufficient insulin - When eating many smaller meals, less glucose enters the blood - less insulin is needed - to return blood glucose to normal OR - A diabetic may not produce sufficient insulin - When eating fewer larger meals, more glucose enters the blood - more insulin is needed - to return blood glucose to normal (4) (10) 3.4 3.4.1 B (1) 3.4.2 - The person is sweating - Vasodilation has occurred (2) (Mark first TWO only) 3.4.3 Adrenalin (1) 3.4.4 - Blood vessels are constricted - Less blood is sent to the skin/sweat glands - Less sweat is formed/less evaporation occurs - and less heat is lost Any (3) (7) [40] TOTAL SECTION B: 80 Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 8 DBE/November 2018 NSC – Marking Guidelines QUESTION 4 The causes of rapid global warming (H) - The concentration of greenhouse gases in the atmosphere has increased - The burning of fossil fuels/use of vehicles/fires - and industrial processes - have released large amounts of CO 2 /N 2 O/CFC’s into the atmosphere - Deforestation - results in less CO 2 being removed from the atmosphere - Due to the decomposition of organic waste in landfills/rice paddies - and the increased number of livestock - the concentration of methane/CH 4 in the atmosphere has increased - This has caused the enhanced greenhouse effect - More heat is trapped in the atmosphere Any (8) Impact of global warming on weather patterns (W) - Higher temperaturesoccur - Heat waves occur - The distribution of rainfall changes - leading to increased rainfall in some areas - while other areas will have decreased rainfall/experience droughts - Storms are more severe/frequent Any (3) How changes in weather patterns affects food security (F) - Food security decreases* Changes in rainfall patterns cause: - Desertification - increased flooding - and wildfires - which increases soil erosion resulting in: o fewer crops to be planted o lower crop yields o less food for livestock - Higher environmental temperatures negatively affects livestock/crops - These factors further decrease food availability - Food becomes more expensive 1*compulsory + Any other 5 (6) Content: (17) Synthesis: (3) (20) Copyright reserved Please turn over

Downloaded from hlayiso.com Life Sciences/P1 9 DBE/November 2018 NSC – Marking Guidelines ASSESSING THE PRESENTATION OF THE ESSAY Relevance Logical sequence Comprehensive All information provided is relevant Ideas arranged in a logical/ cause- Answered all aspects required by to the question effect sequence the essay in sufficient detail All the information provided is All the information regarding the: relevant to: At least the following points should - The causes of rapid global - The causes of rapid global be included: warming warming - The causes of rapid global - The impact of global warming - The impact of global warming warming (H) (5/8) on weather patterns on weather patterns - The impact of global warming - How changing weather patterns - How changing weather patterns on weather patterns (W) (2/3) affect food security affect food security - How changing weather patterns is arranged in a logical manner. affect food security (F) (4/6) There is no irrelevant information 1 mark 1 mark 1 mark TOTAL SECTION C: 20 GRAND TOTAL: 150 Copyright reserved